Band gap engineered ternary semiconductor PbxCd1−xS: Nanoparticle-sensitized solar cells with an efficiency of 8.5%under 1% sun—A combined theoretical and experimental study
PATSORN BOON-ON1*, Shang-Wei Lien2, Tay-Rong Chang2,3,4, Jen-Bin Sh5, Ming-Way Lee1
1Department of Physics, Institution of Nanoscience, Taichung, Taiwan
2Physics, Department of Physics, Tainan, Taiwan
3Department of Physics, Center for Quantum Frontiers of Research &Technology (QFort), Tainan, Taiwan
4Physics, Physics division, Hsinchu, Taiwan
5Electrical Engineering, Department of Electrical Engineering, Taichung, Taiwan
* Presenter:PATSORN BOON-ON,
We report the synthesis and photovoltaic properties of a ternary metal sulfidealloyed semiconductor PbxCd1−xS prepared by the two-stage sequential ionic layeradsorption reaction. The synthesized PbxCd1−xS nanoparticles (NPs) retain the hexag-onal structure of the CdS host with Pb substituting a fraction of the Cd atom (x =0-0.17). Band structures of PbxCd1−xS with various Pb contents x were calculated usingthe complementary density functional theory (DFT) method. Optical, quantum effi-ciency, cyclic voltammetry measurements, and band structure calculation revealedthat the band gap of PbxCd1−xS decreased with increasing x, resulting in an increasedoptical absorption band from 500 to 720 nm (1.73-2.44 eV) for x = 0 to 0.17. Solid-state PbxCd1−xS semiconductor nanoparticle-sensitized solar cells (NSSCs) were fab-ricated from the synthesized NPs using spiro-OMeTAD as the hole-transportingmaterial. The best Pb0.05Cd0.95S cell yielded a power conversion efficiency (PCE) of3.67%, a Vocof 0.70 V, and a fill factor (FF) of 62.8% under 1 sun. The PCE increasedto 5.93% under a reduced light intensity of 0.1 sun and further increased to 8.48%under 0.01 sun. The external quantum efficiency (EQE) spectrum covers the spectralrange of 300 to 730 nm with a maximal EQE of 82% at λ = 580 nm. The PCE over8% can be categorized into a high-efficiency NSSCs. In addition, the Vocof 0.70 V isa relatively high Vocamong all NSSCs. The high PCE and Vocsuggest that PbxCd1−xShas potential to be an efficient solar absorber.

Keywords: cadmium sulfide, lead cadmium sulfide, quantum dot, SILAR, solar cell